Fluid Pump With Shim And Related Methods Of Manufacture

ABSTRACT

A fluid pump includes a gear housing with a pocket wall and a base. The pocket wall and the base define a pocket that projects into the gear housing from a pocket surface. The fluid pump also includes a first gear rotatably positioned in the pocket. The first gear is spaced from the pocket surface by a first gap. The fluid pump also includes a second gear rotatably positioned in the pocket that engages the first gear. The second gear is spaced from the pocket surface by a second gap. The fluid pump also includes a selected shim that is selected from a plurality of shims in a shim set. The selected shim has a thickness that results in a desired clearance between the selected shim and the first face or the second face.

FIELD

The present disclosure relates to a fluid pump that includes a shim and related methods of manufacture.

BACKGROUND

This section provides background information related to the present disclosure which is not necessarily prior art.

Gear pumps include one or more gears that rotate within a gear housing to displace a fluid from an inlet of the pump to an outlet of the pump. The relative spacing of the gears and other components inside the gear housing is a factor that can determine the efficiency and reliability of the gear pump.

In some types of gear pumps, the gears and other internal components are physically stacked next to each other in the gear housing. It is desirable to maintain a desired clearance between the stacked components so that unwanted fluid leakage is minimized. In addition, the desired clearance ensures that the gear (or gears) in the pump can freely rotate during operation. To achieve a desired clearance, various types of traditional manufacturing methods are used to manufacture the components in the pump with tight tolerances such as machining, grinding, polishing and the like. Such manufacturing methods that achieve the tight tolerances can be expensive and time consuming processes. In addition, the stack-up of tolerances of the pump components can increase the variation between pumps assembled with components manufactured according to the same specifications.

There exists a need, therefore, for a pump design that can be assembled with a repeatable desired clearance between internal components. In addition, there is a need for a fluid pump that minimizes unwanted internal leakage of fluid and that can be manufactured with less variation.

SUMMARY

This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features.

In one example embodiment of a fluid pump in accordance with the present disclosure, the fluid pump includes a gear housing with a pocket wall and a base. The pocket wall and the base define a pocket that projects into the gear housing from a pocket surface. The base is oriented parallel to the pocket surface and the pocket wall connects the pocket surface to the base. The fluid pump also includes a first gear rotatably positioned in the pocket. The first gear includes a first face that is oriented parallel to the pocket surface. The first face is spaced from the pocket surface by a first gap. The fluid pump also includes a second gear rotatably positioned in the pocket that engages the first gear. The second gear includes a second face that is oriented parallel to the pocket surface. The second face is spaced from the pocket surface by a second gap. The fluid pump also includes a selected shim positioned in the pocket over the first gear and the second gear. The selected shim is selected from a plurality of shims in a shim set by comparing thicknesses of the shims in the plurality of shims to the first gap or the second gap. The selected shim has a thickness that results in a desired clearance between the selected shim and the first face or the second face.

Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure.

FIG. 1 is a schematic representation of an engine exhaust system in accordance with the present disclosure;

FIG. 2 is an exploded view of an example pump assembly with an example fluid pump head in accordance with the present disclosure;

FIG. 3 is a perspective view of the example fluid pump head shown in FIG. 2;

FIG. 4 is an exploded view of the example fluid pump head of FIG. 3;

FIG. 5 is a sectional view of the example fluid pump head of FIG. 3 cut as indicated on FIG. 3;

FIG. 6 is a perspective view of the example fluid pump head of FIG. 3 shown without the shim; and

FIG. 7 is a process flow diagram of one example method of assembling the example fluid pump head of FIG. 3 in accordance with the present disclosure.

Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings.

DETAILED DESCRIPTION

Example embodiments will now be described more fully with reference to the accompanying drawings.

FIG. 1 schematically illustrates an example exhaust system 10. Exhaust system 10 can include at least an engine 12 in communication with a fuel source (not shown) that, once consumed, will produce exhaust gases that are discharged into an exhaust passage 14 having an exhaust after-treatment system 16. Downstream from engine 12 can be disposed a pair of exhaust treatment components 18 and 20, which can include catalyst-coated substrates or filters 22 and 24. Catalyst-coated substrates or filters 22 and 24 can be any combination of a diesel particulate filter (DPF), a diesel oxidation catalyst (DOC) component, a selective catalytic reduction (SCR) component, a lean NOX catalyst, an ammonia slip catalyst, a catalyst-coated (e.g., SCR or DOC) DPF, NOX absorber, CO2 capture catalyst, or any other type or combination of exhaust treatment devices known to one skilled in the art.

Although not required by the present disclosure, exhaust after-treatment system 16 can further include components such as a thermal enhancement device or burner 26 to increase a temperature of the exhaust gases passing through exhaust passage 14. Increasing the temperature of the exhaust gas is favorable to achieve light-off of the catalyst in the exhaust treatment component 18 in cold-weather conditions and upon start-up of engine 12, as well as initiate regeneration of the exhaust treatment component 18 when the exhaust treatment substrate 22 or 24 is a DPF.

To assist in reduction of the emissions produced by engine 12, exhaust after-treatment system 16 can include a dosing module 28 for periodically dosing an exhaust treatment fluid into the exhaust stream. As illustrated in FIG. 1, the dosing module 28 can be located upstream of exhaust treatment component 18, and is operable to inject an exhaust treatment fluid into the exhaust stream. In this regard, the dosing module 28 is in fluid communication with a reagent tank 30 and a pump 32 by way of inlet line 34 to dose an exhaust treatment fluid such as diesel fuel or urea into the exhaust passage 14 upstream of exhaust treatment components 18 and 20. Dosing module 28 can also be in communication with reagent tank 30 via return line 36. Return line 36 allows for any exhaust treatment fluid not dosed into the exhaust stream to be returned to reagent tank 30. Flow of the exhaust treatment fluid through inlet line 34, dosing module 28, and return line 36 also assists in cooling dosing module 28 so that dosing module 28 does not overheat. Although not illustrated in the drawings, dosing module 28 can be configured to include a cooling jacket that passes a coolant around dosing module 28 to cool it.

The amount of exhaust treatment fluid required to effectively treat the exhaust stream may vary with load, engine speed, exhaust gas temperature, exhaust gas flow, engine fuel injection timing, desired NOx reduction, barometric pressure, relative humidity, EGR rate and engine coolant temperature. A NOx sensor or meter 38 may be positioned downstream from exhaust treatment component 18. NOx sensor or meter 38 may also be positioned upstream or between the exhaust treatment components 18 and 20. NOx sensor 38 is operable to output a signal indicative of the exhaust NOx content to an engine control unit 40. NOx sensor or meter 38 may also be replaced by a particulate matter sensor. All or some of the engine operating parameters may be supplied from engine control unit 40 via the engine/vehicle databus to a reagent electronic dosing controller 42. The reagent electronic dosing controller 42 could also be included as part of the engine control unit 40. Exhaust gas temperature, exhaust gas flow and exhaust back pressure and other vehicle operating parameters may be measured by respective sensors, as indicated in FIG. 1.

The amount of exhaust treatment fluid required to effectively treat the exhaust stream can also be dependent on the size of the engine 12. In this regard, large-scale diesel engines used in locomotives, marine applications, and stationary applications can have exhaust flow rates that exceed the capacity of a single dosing module 28. Accordingly, although only a single dosing module 28 is illustrated for dosing exhaust treatment fluid, it should be understood that multiple dosing modules 28 for reagent injection are contemplated by the present disclosure.

As described, the pump 32 can be any suitable fluid pump for dosing the exhaust treatment fluid into the exhaust stream. One suitable type of pump 32 is a gear pump. As depicted in FIG. 2, pump 32, in one example, can include a motor casing 50 and a filter casing 52 that surround a fluid pump head 60. The motor casing 50 can be positioned over a portion of the fluid pump head 60 and is mechanically or electrically coupled thereto to cause the gears of the fluid pump head 60 to rotate and cause movement of a fluid therethrough.

The filter casing 52, in this example, is also positioned over a portion of fluid pump head 60. The filter casing 52 can include a filter assembly (not shown) that can be in fluid communication with the fluid pump head 60 to filter contaminants from the fluid contained in or flowing through the pump 32 during operation. The filter casing 52 and the motor casing 50 can be joined to each other to surround the fluid pump head 60 as shown. In other examples, the pump 32 can include other configurations and/or casings and may include other assemblies that can be joined to the fluid pump head 60.

FIGS. 3-6 show one example of a fluid pump head 60 in accordance with the present disclosure. The fluid pump head 60 includes a gear housing 62, a cover plate 64, a shim 66, a first gear 68, a second gear 70, and a gear guide 72.

The gear housing 62, as shown in FIG. 3, is cylindrical in this example and includes a pocket 74. The pocket 74 is a recessed feature of the gear housing 62 defined by a pocket wall 76 and by a base 78. The pocket 74 is shaped so that it can receive the first gear 68, the second gear 70, the gear guide 72 and the shim 66. To this end, the pocket 74 includes a first circular depression 80 and a second circular depression 82. The first circular depression 80 and the second circular depression 82 intersect at or near the center of the gear housing 62 to create a two-lobed shape. With this shape, the first gear 68 can be positioned in the first circular depression 80 and the second gear 70 can be positioned in the second circular depression 82.

The gear housing 62 further includes, in this example, a first inlet 94 and a first outlet 96. The first inlet 94 and the first outlet 96 are openings that extend through the gear housing 62 to fluidly connect the pocket 74 to a fluid source, a fluid conduit, a nozzle or other element that may be connected to the fluid pump head 60. When the fluid pump head 60 is operating, the fluid flowing through the fluid pump head 60 enters through the first inlet 94 and exits through the first outlet 96.

The fluid pump head 60 can be made of any suitable material. In this example, the gear housing 62 is made of stainless steel. The gear housing 62 can be cast and then machined into the configuration described. In another example, the gear housing 62 can be machined from stainless steel bar stock. In other examples, other metals, alloys, plastics and composites can also be used.

As shown in FIG. 4, the first gear 68 and the second gear 70 are positioned, in this example, on the gear guide 72. The gear guide 72 includes a footing 84, a first post 86 and a second post 88. The footing 84 is a planar member that has a profile similar to the shape of the pocket 74. In this example, the footing 84 of the gear guide 72 has a two-lobed shape with a first lobe 90 connected to a second lobe 92. As such, the gear guide 72 can fit within the pocket 74. The footing 84 is sized so that the first lobe 90 and the second lobe 92 fit within the first circular depression 80 and the second circular depression 82, respectively, and restrict lateral movement of the gear guide 72 when the gear guide 72 is installed into the pocket 74. The gear guide 72 can be positioned in the pocket 74 such that the footing 84 abuts the base 78.

The first post 86 and the second post 88, in this example, are cylindrical features of the gear guide 72 that project away from the footing 84. The first post 86 is located at or near the center of the first lobe 90 and the second post 42 is located at or near the center of the second lobe 92. In this manner, the first post 86 and the second post 88 are located at or near the center of the first circular depression 80 and the second circular depression 82 when the gear guide is installed in the pocket 74.

The first post 86 and the second post 88 are spaced apart from one another such that the first gear 68 and the second gear 70, when received over the first post 86 and the second post 88, respectively, engage with one another. When installed over the first post 86 and the second post 88, the first gear 68 rotates around the first post 86 and the second gear 70 rotates around the second post 88. As shown in FIG. 5, the first post 86 projects away from the footing 84. The first post 86 has a height, as measured along a center axis 160 from the base 78, that positions a top of the post 86 within the pocket 74 above the first gear 68 (i.e., at or near an axial position of the shim 66). The second post 88 can have a similar height to the height of the first post 86. The gear guide 72, in this example, is made of a suitable ceramic material. In other examples, other materials, such as stainless steel, can also be used.

Referring back to FIG. 4, the first gear 68 includes a first bore 98 and the second gear 70 includes a second bore 100. The first bore 98 is a cylindrical aperture that extends through the center of the first gear 68. The inner diameter of the first bore 98 is greater than the outer diameter of the first post 86. As such, the first gear 68 can be received over the first post 86 and rotate around the first post 86. The second bore 100 of the second gear 70 is similarly configured with respect to the second post 88. The inner diameter of the second bore 100 is greater than the outer diameter of the second post 88. In this configuration, the second gear 70 can be received over and rotate around the second post 88.

The first gear 68 includes teeth 102 and the second gear 70 includes teeth 152. The teeth 102 of the first gear 68 and the teeth 152 of the second gear 70 are sized such that they can mesh and engage with one another to displace fluid in the pocket 74 of the gear housing 62 when the first gear 68 and the second gear 70 rotate around the first post 86 and the second post 88, respectively.

The teeth 102 and the profile of the first gear 68 and the teeth 152 and the profile of the second gear 70 can be similar to one another. In the example shown, the teeth 102 have a rounded triangular shape. The first gear 68 and the second gear 70 each have nine teeth 102, 152 evenly spaced around their peripheries. In other examples, the teeth 102, 152 can have other shapes and the first gear 68 and/or the second gear 70 can more or less than nine teeth 102, 152.

The first gear 68, as shown in the example of FIG. 4, has an engaging portion 104 and a drive extension 106. The drive extension 106 is a cylindrically-shaped portion of the first gear 68. The drive extension 106 projects away from the engaging portion 104. The drive extension 106 is positioned at the center of the first gear 68. At a distal end of the drive extension 106, the drive extension 106 includes a plurality of drive teeth 108. As can be appreciated and as shown in FIG. 3, the drive extension 106 projects out of the gear housing 62 when the fluid pump head 60 is assembled so that the first gear 68 can be mechanically coupled to a motor (not shown) to induce rotation of the first gear 68. The drive teeth 108 are sized and otherwise configured to advantageously engage a complimentary gear of the motor (not shown) to turn the first gear 68 in the gear housing 62. This movement of the first gear 68, in turn, causes the second gear 70 to rotate in the gear housing 62.

The second gear 70, in the example shown, includes a second engaging portion 110 and a collar 112. The second engaging portion 110 is the portion of the second gear that includes the teeth 102 that engage the teeth 102 of the first gear 68. The collar 112 is a circular boss that projects away from the second engaging portion 110. The collar 112 can be used to interface with the shim 66 (as will be explained further below) or other element of the fluid pump head 60 to maintain the second gear 70 in a desired position in the pocket 74. To this end, the collar 112 is positioned at or near the center of the second gear 70.

The first gear 68 and the second gear 70 can be made of any suitable material. In this example, the first gear 68 and the second gear 70 are made of polyether ether ketone (PEEK). This material has mechanical and chemical resistant properties at high temperatures. Other materials, such as stainless steel, can also be used.

The shim 66, in this example, is located in the pocket 74 and is inserted over the first gear 68 and the second gear 70. The shim 66 has a two-lobed profile and includes a first ring 114 and a second ring 116. The shim 66 is sized such that the outer diameter of the first ring 114 is less than the inner diameter of the first lobe 90 of the pocket 74. The outer diameter of the second ring 116 is less than the inner diameter of the second lobe 92 of the pocket 74.

The shim 66 also includes a first aperture 118 and a second aperture 120. The first aperture 118 is positioned at or near the center of the first ring 114. The inner diameter of the first aperture 118 is greater than the outer diameter of the drive extension 106. The second aperture 120 is positioned at or near the center of the second ring 116. The inner diameter of the second aperture 120 is greater than outer diameter of the collar 112. With this configuration and as shown in FIG. 3, the shim 66 can be inserted into the pocket 74 and over the drive extension 106 of the first gear 68 and over the collar 112 of the second gear 70.

The shim 66 can also include a first notch 122 and/or a second notch 124. The first notch 122 and the second notch 124, in the example shown in FIG. 3, are rounded cut-outs located at the intersection of the first ring 114 and the second ring 116. The first notch 122 and the second notch 124 are positioned on opposite sides of the shim 66 and are located to fluidly connect with the first inlet 94 and the first outlet 96, respectively. In this configuration, the first notch 122 can define a first port 126 and the second notch 124 can define a second port 128. The first inlet 94 and the first port 126 are in fluid communication on one side of the gear housing 62. Similarly, the first outlet 96 and the second port 128 are in fluid communication on an opposite side of the gear housing 62.

As shown, the shim 66, the first gear 68, the second gear 70 and the gear guide 72 are located in the pocket 74. These components stack inside in the pocket 74 such that the shim 66 does not project beyond a pocket surface 130 of the gear housing 62. As can be appreciated, the shim 66, the first gear 68, the second gear 70 and the gear guide 72 are located within the pocket 74 and do not project beyond the pocket surface 130 because interference between these components and the cover plate 64 is undesirable. When the cover plate 64 is installed over the pocket 74, interference between the shim 66, the first gear 68, the second gear 70 or the gear guide 72 and the cover plate 64 can cause inefficiencies if the components were to bind or otherwise contact one another.

As shown in FIGS. 4 and 5, the cover plate 64 is installed over the pocket 74 and adjacent to the pocket surface of the gear housing 62. The gear housing 62 can include one or more attachment holes 132. The cover plate 64 can include one or more openings 134 that are configured to align with the attachment holes 132. Fasteners can be inserted through the openings and secured in the attachment holes 132 to secure the cover plate 64 in position over the pocket 74. The gear housing 62 can include a groove 136 into which a seal (not shown) is inserted. The seal can be compressed between the gear housing 62 and the cover plate 64 in the groove 136 to fluidly seal the gear housing 62. Other arrangements and configurations can also be used to cover and seal the gear housing 62.

In another example of the fluid pump head 60, the cover plate 64 can be positioned over the pocket 74 such that a portion of the cover plate 64 can be separated from the pocket surface 130 of the gear housing 62. In such examples, the shim 66 can project above the pocket surface 130 and into the portions of the cover plate 64 that may be separated from the pocket surface 130. In these examples, the stack up of the components positioned in the pocket 74 (i.e., the gear guide 72, the first gear 68, the second gear 70 and the shim 66) is configured so that a desired clearance is maintained between the components to ensure efficient and reliable operation.

Referring back to the example shown in FIGS. 3 and 4, the shim 66 can include a first channel 138, a second channel 154 and a third channel 156. The channels 138, 154, 156 are elongated recessed pathways that extend along the surface of the shim 66. The channels 138, 154, 156 permit fluid to move from one location on the shim 66 to a second location on the shim 66. As shown in this example, the first channel 138 extends between the first aperture 118 and the second aperture 120 across the middle portion of the shim 66. This channel 138 permits fluid to move along this path in order to reduce pressure pulsation in the fluid pump head 60 when the first gear 68 and the second gear 70 engage. The shim 66 also includes the second channel 154 that extends between the first aperture 118 and the second port 128 and the third channel 156 that extends between the second aperture 120 and the second port 128. The second channel 154 and the third channel 156 permit fluid to flow along this path to ensure that the components of the fluid pump head 60 are lubricated. The channels 138 can be located on both sides of the shim 66. In other examples, the shim 66 can include other channels or channels with different pathways.

As shown in FIG. 4, the gear guide 72 can also include one or more guide channels 158. In the example shown, the gear guide 72 includes a guide channel 158 that extends between the first post 86 and the second post 88. The gear guide 72 can also include a guide channel 158 that extends between the first post 86 and the first port 126 and another that extends between the second post 88 and the first port 126. These channels 158 can serve the same or a similar purpose as that previously described. The first post 86 and the second post 88 can include a channel that encircles the first post 86 and/or the second post 88. In this configuration, the region of the first post 86 and/or the second post 88 that connects to the footing 84 can be lubricated to facilitate the rotation of the first gear 68 and/or the second gear 70. In other examples, the gear guide 72 can include other configurations and arrangements of channels in order to improve efficiency of the fluid pump head 60 and/or to prevent pressure pulsation or cavitation.

In the example of FIGS. 3-6, the gear housing 62 can include an offset portion 140. As shown in FIG. 5, the offset portion 140 is fluidly connected to the pocket 74 by a passage 142. The passage 142 extends from the base 78 to the offset portion 140. The offset portion 140 is configured to receive a filter assembly (not shown) that can be connected to the fluid pump head 60. The filter assembly can be fluidly connected to the fluid pump head 60 by the passage 142 and/or other passageways in order to deliver fluid through the drive extension 106 in order to lubricate the drive extension 106 and the motor components that may be coupled thereto. As can be appreciated, the offset portion 140 aligns the filter assembly and/or the filter casing 52 with the motor and/or the motor casing 50 to reduce the overall envelope size of the pump 32. In other examples, the fluid pump head 60 may not include an offset portion 140 or may have other shapes or features to connect the fluid pump head 60 to other elements of the pump 32.

As further shown in FIG. 5, and as previously described, the gear guide 72, the first gear 68 and the shim 66 stack inside the pocket 74 and are covered by the cover plate 64. The footing 84 of the gear guide 72 has a thickness of T1. The first gear 68 has a thickness of T2 and the shim 66 has a thickness of T3. The pocket 74 has a height of H1. When the gear guide 72, the first gear 68 and the shim 66 are assembled into the pocket 74, a desired clearance C can be achieved between the first gear 68 and the shim 66.

It is desirable that the stack-up of the thicknesses of the footing 84, the first gear 68 and the shim 66 (T1+T2+T3) is less than the height H1. As previously described, if the stack-up of the thicknesses of the footing 84, the first gear 68 and the shim 66 are greater than the height H1 of the pocket 74, the components can bind or interfere and cause inefficiencies in the fluid pump head 60.

It is also desirable that clearances between the gear guide 72, the first gear 68, the shim 66 and the cover plate 64 are minimized. The reduction of the clearance between these components reduces leakage that may otherwise occur between these components. Internal leakage between these components can lead to inefficiencies in the fluid pump head 60.

One way of achieving the desired clearance C and minimizing the clearances between the components is to control the variation of the thickness of the gear guide 72, the first gear 68, the shim 66 and the height of the pocket 74. Since the gear guide 72, the first gear 68 and the shim 66 are stacked next to each other, the variation of the stacked thickness is difficult to control since the tolerances associated with the thicknesses of the individual components are also stacked with each other. The control of tight tolerances for the thicknesses of the gear guide, the first gear 68, the shim 66 and the height of the pocket 74 can be expensive and time consuming.

Instead of specifying tight or reduced tolerances for the thicknesses of the gear guide 72, the first gear 68, the shim 66 and/or the height of the pocket 74, one method of assembling the fluid pump head 60 to achieve a desired clearance C in accordance with the present disclosure includes measuring a gap after one or more of the components is assembled into the pocket 74 and then choosing a shim 66 from a plurality of shims with different thicknesses to obtain the desired clearance C.

As shown in FIG. 6, the fluid pump head 60 is shown in an intermediate stage of assembly. At this stage, the gear guide 72, the first gear 68 and the second gear 70 have been inserted into the pocket 74 of the gear housing 62. The first gear 68 includes a first face 148 that is the surface of the engaging portion 104 of the first gear 68 that is oriented away from the base 78 of the pocket 74. The first face 148 is spaced apart from the pocket surface 130 of the gear housing 62 by a first gap 144. The first gap 144 is measured along the pocket wall 76 in a direction parallel to the center axis 160 of the first post 86.

Similarly, the second gear 70 has a second face 150. The second face 150 is a surface of the second engaging portion 110 of the second gear 70 that is oriented away from the base 78 of the pocket 74. The second face 150 is spaced apart from the pocket surface of the gear housing 62 by a second gap 146. The second gap 146 is measured along the pocket wall 76 in a direction parallel to the center axis of the first post 86.

The first gap 144 and/or the second gap 146 can be measured during the assembly process. A gauge, micrometer, coordinate measuring machine (CMM) or caliper can be used to measure the first gap 144 and/or the second gap 146. After determining the first gap 144 and/or the second gap 146, an appropriately sized shim 66 can be selected from a plurality of shims with varying thicknesses such that when the selected shim is inserted into the pocket 74, the resulting clearance is the desired clearance C.

A shim set (not shown) can be supplied to aid in the previously described assembly process. The shim set can be a bundle of the shims 66. The shims 66 have varying thicknesses T3. In one example fluid pump head 60, the desired clearance C is approximately 20 microns. To achieve this desired clearance, the shim set can include shims 66 that vary in thickness from 0.5 mm to 0.71 mm. The shims 66, in this example shim set, would each have a thickness that varies by approximately 3 microns. In another example, the shim set can be a bundle consisting of ten to fifteen of the shims 66. The ten to fifteen shims 66, in this alternate example, each have a different thickness T3 that varies between 0.5 mm to 1.5 mm. In this example, the shim set consists of shims 66 having thickness T3 of 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1.0 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm and 1.5 mm. In other examples, there can be more than fifteen shims in the shim set or there can be less than ten shims in the shim set. The shims in the shim set can have other variations in thicknesses T3 as well. As can be appreciated, for different sizes of the fluid pump head 60, the size and thicknesses of the shims 66 in the shim set can be different to accommodate larger or smaller fluid pump heads 60. In still other examples, the pump head 60 can be assembled with gear guides 72 with differing thicknesses T1 of the footing 84 to achieve a desired clearance C or to accommodate different shim sets or different sizes of the pump head 60.

The shims 66 can be made of any suitable material such as ceramic or stainless steel. In other examples, other materials can also be used. In order to achieve the necessary varying thicknesses of the shims 66, a grinding or lapping operation can be used to produce the shims 66. In other examples, other processes can be used.

In another example of the fluid pump head 60, the first gap 144 and/or the second gap 146 can be measured relative to a pocket side 162 of the cover plate 64. The pocket side 162 of the cover plate 64 is the surface of the cover plate 64 oriented toward the gear housing 62. In the example shown in FIG. 5, the pocket side 162 is adjacent to the pocket surface 130 of the gear housing 62. In other examples, the pocket side 162 of the cover plate 64, or a portion thereof, may be separated from the pocket surface 130. In such examples, the first gap 144 can be measured as the distance between the first face 148 of the first gear 68 and the pocket side 162 of the cover plate 64. Similarly, the second gap 146 can alternatively be measured as the distance between the second face 150 of the second gear 70 and the pocket side 162 of the cover plate 64. The first gap 144 and/or the second gap 146, measured in relation to the cover plate 64, can be used to select a shim 66 from the shim set as previously described.

FIG. 7 shows one example method of assembly of the fluid pump head 60. At step 170, the gear guide 72 is inserted into the pocket 74 of the gear housing 62. The gear guide 72 sits in the pocket 74 with the footing 84 abutting the base 78. At step 172, the first gear 68 is installed over the first post 86 of the gear guide 72. At step 174, the second gear 70 is installed over the second post 88 of the gear guide 72. At this stage of the process, the fluid pump head 60, in this example, appears as shown in FIG. 6.

At step 176, the first gap 144 is measured. As described, the first gap 144 is a height between the first face 148 and the pocket surface 130 measured in the direction parallel to the center axis 160 of the first post 86. Alternatively, the first gap 144 can be measured as the height between the first face 148 and the pocket side 162 of the cover plate 64.

At step 178, the second gap 146 is measured. As described, the second gap is a height between the second face 150 and the pocket surface measured in the direction parallel to the center axis 160 of the first post 86. Alternatively, the second gap 146 can be measured as the height between the second face 150 and the pocket side 162 of the cover plate 64.

At step 180, the measured first gap 144 is compared to the measured second gap 146. The smaller of the first gap 144 and the second gap 146 is used in the subsequent steps of the process. As can be appreciated, the shim 66 that is selected at the later steps is smaller than the first gap 144 or the second gap 146 if the desired clearance is to be achieved. Therefore, at step 180, the first gap 144 is compared to the second gap 146 to determine which of the first gap 144 and the second gap 146 is smaller.

At step 182, the smaller of the first gap 144 and the second gap 146 is compared to the thicknesses of the shims 66 in the shim set. As described above, the shim set includes a plurality of shims of varying thicknesses.

At step 184, the shim 66 with a thickness closest to but less than the smaller of the first gap 144 and the second gap 146 is selected from the shim set. Alternatively, at step 184, the shim 66 can be selected from the shim set so that the desired clearance C is achieved. In one example, the desired clearance is a minimum clearance.

At step 186, the selected shim 66 is inserted into the pocket 74 over the first gear 68 and the second gear 70. At step 188, the cover plate 64 is installed over the pocket 74 to retain the gear guide 72, the first gear 68, the second gear 70 and the shim 66 inside the gear housing 62.

As can be appreciated, one or more of the previously described steps of the example method can be excluded. In addition, additional steps can be performed. Such alterations to the previously described method may be desirable or advantageous in other example embodiments of the fluid pump head 60.

In one such alternate example of the fluid pump head 60 (not shown), the fluid pump head 60 does not include a separate gear guide 72. In this alternate example, the first post 86 and the second post 88 can be press fit or otherwise secured in the base 78 of the pocket 74. The first post 86 and the second post 88 can be similarly configured as previously described. In this example, the first gear 68 and the second gear 70 are positioned directly adjacent the base 78 of the pocket 74 over the first post 86 and the second post 88, respectively. The shim 66, as previously described, can still be used in this example to achieve a desired clearance C between the first gear 68 and/or the second gear 70 and the shim 66.

In still another example, the second gear 70 is not positioned on the second post 88. In this example, the second gear 70 is positioned in the second circular depression 82 of the pocket 74 without a supporting axial member (e.g., second post 88). The second gear 70 is retained in its position by the pocket wall 76 and its engagement to the first gear 68. In this example, the shim 66 does not include a second aperture 120. Instead, the second ring 116 is a planar member that covers the second lobe 92 of the pocket 74. The shim 66 can still be used to achieve a desired clearance C between the first gear 68 and/or the second gear 70 and the shim 66.

The previously described fluid pump head 60, and variations thereof, advantageously reduces the amount of internal leakage in the fluid pump head 60 by reducing the clearances between the internal components. This reduction increases the efficiency of the fluid pump head 60 and also reduces the variation from pump to pump. The foregoing fluid pump head 60 and the related method of manufacture also reduce the likelihood of interference or binding of internal components. Given that the structure of the fluid pump head 60 and the related method of manufacture ensure that the desired clearance between the internal components is maintained, it may also be possible to reduce the size and/or power of the pump motor that is used to drive the fluid pump head 60. These improvements can reduce the cost and increase the reliability of the fluid pump head 60.

As can be appreciated, the fluid pump head 60 can be used in a variety of applications. In the example application previously described, the fluid pump head 60 is used in the exhaust system 10. The fluid pump head 60, however, can be used to transfer fuel, oil or other fluids as well. In addition, the fluid pump head 60 can be used in a variety of industrial applications including in the automotive, chemical, manufacturing, and energy industries.

The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.

Example embodiments are provided so that this disclosure will be thorough, and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure. In some example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an,” and “the” may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises,” “comprising,” “including,” and “having,” are inclusive and therefore specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed.

When an element or layer is referred to as being “on,” “engaged to,” “connected to,” or “coupled to” another element or layer, it may be directly on, engaged, connected or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly engaged to,” “directly connected to,” or “directly coupled to” another element or layer, there may be no intervening elements or layers present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between,” “adjacent” versus “directly adjacent,” etc.). As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.

Although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer or section from another region, layer or section. Terms such as “first,” “second,” and other numerical terms when used herein do not imply a sequence or order unless clearly indicated by the context. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the example embodiments.

Spatially relative terms, such as “inner,” “outer,” “beneath,” “below,” “lower,” “above,” “upper,” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. Spatially relative terms may be intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the example term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. 

What is claimed is:
 1. A fluid pump comprising: a gear housing including a pocket wall and a base, the pocket wall and the base defining a pocket that projects into the gear housing from a pocket surface; a first gear rotatably positioned in the pocket, the first gear including a first face that is spaced from the pocket surface by a first gap; a second gear rotatably positioned in the pocket and engaging the first gear, the second gear including a second face that is spaced from the pocket surface by a second gap; and a selected shim positioned in the pocket over the first gear and the second gear, wherein the selected shim is selected from a plurality of shims in a shim set by comparing thicknesses of the shims in the plurality of shims to the first gap or the second gap, the selected shim having a thickness that results in a desired clearance between the selected shim and the first face or the second face.
 2. The fluid pump of claim 1 wherein the desired clearance is a minimum clearance.
 3. The fluid plump of claim 1 wherein the pocket wall includes two rounded portions to define a pocket with a first circular depression and a second circular depression, the first circular depression configured to receive the first gear and the second circular depression configured to receive the second gear.
 4. The fluid pump of claim 1 further comprising a gear guide positioned in the pocket, the gear guide including a first post projecting upward in the pocket toward the pocket surface and a second post projecting upward in the pocket toward the pocket surface, the first post configured to receive the first gear and the second post configured to receive the second gear.
 5. The fluid pump of claim 3 wherein the selected shim includes a first ring and a second ring, the first ring positioned over the first gear in the first circular depression and the second ring positioned over the second gear in the second circular depression.
 6. The fluid pump of claim 1 further comprising a cover plate removably attached to the gear housing adjacent to the pocket surface and covering the pocket.
 7. The fluid pump of claim 1 wherein, when the first gap is greater than the second gap, the selected shim is selected by comparing the thickness of the shims in the plurality of shims to the second gap.
 8. The fluid pump of claim 1 wherein the plurality of shims includes at least five shims having different thicknesses.
 9. The fluid pump of claim 8 wherein the thicknesses of the plurality of shims vary from 0.5 mm to 1.5 mm.
 10. The fluid pump of claim 1 wherein the selected shim is selected from the plurality of shims after the first gear and the second gear are installed in the pocket and the first gap and the second gap are measured.
 11. A method of manufacturing a fluid pump comprising: inserting a first gear over a post in a pocket of a gear housing such that a face of the first gear is oriented toward a pocket surface of the gear housing and the first gear is configured to rotate around a center axis of the post; measuring a height of a first gap between the face of the first gear and the pocket surface of the gear housing wherein the height of the first gap is measured in a direction parallel to the center axis; comparing the height of the first gap to thicknesses of shims in a shim set, the shim set comprising a plurality of shims with varying thicknesses; choosing a selected shim from the shim set wherein the thickness of the selected shim results in a desired clearance between the first gear and the selected shim; and inserting the selected shim in the pocket over the first gear.
 12. The method of claim 11 wherein the thickness of the selected shim is closest to and less than the height of the gap.
 13. The method of claim 11 further comprising: inserting a second gear over a second post in the pocket of the gear housing such that a face of the second gear is oriented toward the pocket surface of the gear housing; measuring a height of a second gap between the face of the second gear and the pocket surface of the gear housing wherein the height of the second gap is measured in a direction parallel to the center axis; comparing the height of the second gap to the height of the first gap to determine if the height of the second gap is less than the height of the first gap; and if the height of the second gap is less than the height of the first gap, comparing the height of the second gap to the thicknesses of the shims in the shim set; and choosing the selected shim from the shim set to obtain the desired clearance between the second gear and the selected shim.
 14. The method of claim 11 further comprising inserting a gear guide with the post into the pocket of the gear housing such that the post projects away from a base of the pocket toward the pocket surface and is configured to receive the first gear thereon.
 15. The method of claim 11 wherein the shim set includes at least five shims having different thicknesses.
 16. The method of claim 11 further comprising, securing a cover plate to the gear housing over the pocket, the cover plate configured to retain the first gear and the selected shim in the pocket.
 17. The method of claim 11 wherein the desired clearance is a minimum clearance.
 18. The method of claim 11 wherein, when the selected shim is inserted into the pocket of the gear housing, the selected shim minimizes unwanted leakage of fluid from the pocket.
 19. A fluid pump comprising: a gear housing including a pocket wall and a base, the pocket wall and the base defining a pocket that projects into the gear housing from a pocket surface; a cover plate secured to the gear housing, the cover plate including a pocket side oriented toward the gear housing and over the pocket; a first gear rotatably positioned in the pocket, the first gear including a first face oriented toward the pocket side of the cover plate, wherein the first face is spaced from the pocket side by a first gap; a second gear rotatably positioned in the pocket and engaging the first gear, the second gear including a second face that is oriented toward the pocket side of the cover plate, wherein the second face is spaced from the pocket side by a second gap; and a selected shim positioned in the pocket over the first gear and the second gear, wherein the selected shim is selected from a plurality of shims in a shim set by comparing thicknesses of the shims in the plurality of shims to the first gap or the second gap, the selected shim having a thickness that results in a desired clearance between the selected shim and the first face or the second face.
 20. The fluid pump of claim 19 wherein the pocket surface of the gear housing and at least a portion of the pocket side of the cover plate are separated from one another over the pocket. 